The present invention is directed to an explosive powder charge operated setting tool having a housing equipped with a handle, a piston guide is axially displaceable within and relative to the housing against the force of a spring. A firing pin guide is also located within the housing rearwardly of the piston guide. The firing pin guide is axially displaceable relative to the housing and cooperates with a damping device bearing against a stop face at the trailing end of the housing and directed facing in the driving direction.
An explosive counter-charge operated setting tool is disclosed in EP-O 331 168 A1 which serves for driving fastening elements, such as nails, bolts, studs and the like, into hard receiving materials. A piston guide and a firing pin guide are located within a housing with the firing pin guide located behind the piston guide and both are axially displaceable relative to the housing. The housing includes a handle. The piston guide is displaceable against the force of a spring and the firing pin guide is displaceable against the force of a damping device bearing against a trailing end stop face in the housing. The piston guide projects axially outwardly from a leading end face of the housing and includes a driving piston moveable in a guide bore within the piston guide.
A cartridge chamber is located in a trailing end region of the piston guide facing the firing pin guide. The chamber is arranged to hold an explosive powder cartridge. A firing mechanism located in the firing pin guide includes a firing pin axially displaceable against the force of a spring element. When the setting tool is pressed against a receiving material, the piston guide moves in its axial direction opposite to the driving direction until it rests against the firing pin guide. As a result, the spring element and a spring disposed between the piston guide and the housing are prestressed or preloaded.
If an operating trigger located in the handle is depressed, the firing pin is accelerated in the direction of the cartridge charge by the preloaded spring element and it ignites the cartridge. The propellant gas pressure developed in ignition of the cartridge accelerates the piston guide and the firing pin guide opposite to the driving direction and the driving piston is accelerated in the guide bore of the piston guide in the driving direction, so that the driving piston drives a fastening element located in the muzzle region of the piston guide into the receiving material. The acceleration of the piston guide and the firing pin guide relative to the housing and opposite to the driving direction is damped by the shock absorbing device.
If the pressure developed in the driving operation is great, an axial displacement of the firing pin relative to the housing takes place during the driving operation. This entails at least a partial compression of the damping device. During the subsequent driving operation, the damping device is no longer able to sufficiently damp out the rebound force acting on the housing or the handle. Accordingly, there ia a danger of injury to the tool operator.